by Harriet Baskas, Special for USA TODAY

by Harriet Baskas, Special for USA TODAY

On Sunday, a fight between two passengers over personal space, a thrown cup of water and the use of a controversial plastic gadget that prevents airline seats from reclining caused United Airlines Flight 1462 from Newark, N.J., to Denver to divert to Chicago's O'Hare International Airport, the AP reports.

During the flight, a man seated in the Economy Plus section, which offers four more inches of legroom than other coach seats, was reportedly using a $21.95 gadget called a Knee Defender to prevent the woman seated in front of him from reclining her seat.

While the Federal Aviation Administration does not prohibit the use of the Knee Defender, like most other major U.S. airlines, "we do not allow customers to use devices that prevent seats from reclining," said United Airlines spokesman Charles Hobart via e-mail.

But the male passenger refused to remove the device when asked to do so by the flight attendant.

The woman whose seat could not recline stood up and threw a cup of water at the Knee Defender user, a law enforcement official told AP, and soon after United made the decision to land the plane in Chicago.

"Authorities met the aircraft, removed the two passengers and the flight continued to Denver shortly afterwards," said Hobart.

No arrests were made because the incident "was deemed a customer service issue and not a threat to aviation security," said Transportation Security Administration spokesman Ross Feinstein.

"Sometimes people do things they shouldn't do on airplanes, but as far as I know this is the first time anything like this has happened," involving the Knee Defender, said Ira Goldman, the man who invented the device in 2003 and continues to sell it online.

"United could make seats that do not recline, but they have not chosen to do so," said Goldman. "In the meantime, the Knee Defender says right on it: 'Be courteous. Do not hog space. Listen to the flight crew.' Apparently that is not what happened here."